Head for horizontal boring

ABSTRACT

A head for an auger for horizontal earth boring has four point support which assists in keeping the hole round and in line. The boring head, attached to the working end of an auger shaft has two opposed boring arms formed with tooth holding sockets for replaceable digging teeth and also for a pilot bit. To the rear of the arms is an expansion tooth head having opposed arms intermediate the boring head arms. These arms carry on their outer ends holders for expansion teeth which pivot outward when the auger is rotated in one direction and inward when the auger is reversed. The expansion teeth and outermost boring head teeth are 90* apart and hence the head is supported so that its tendency to bore a hole which is elliptic toward the bottom is overcome. Further, adjustment is provided for the maximum extent of outward pivotting of the expansion tooth holder for different casing wall thicknesses.

United States Patent 1191 Benetti et al.

1 1 May 22,1973

[54] HEAD FOR HORIZONTAL BORING Primary Examiner-Joseph H. McGlynn [75]Inventors: John G. Benetti, Cupertino; Walter Assstam 'f"" Favrea" L.Sturgeon, Los Altos, both of Attorney"juhan Caplan Calif. [57] ABSTRACT[73] Ass1gnee: Pengo Corporation, Sunnyvale,

C lif, A head for an auger for horizontal earth boring has four pointsupport which assists in keeping the hole [22] Flledi Sept 1971 roundand in line. The boring head, attached to the [21] Appl. No.: 183,326working end of an auger shaft has two opposed boring arms formed withtooth holding sockets for replacea- 52 US. Cl. ..17s/3s4 175/171 175/62ble digging teeth and a PM the 299/86 the arms is an expansion toothhead having opposed 51 1m. (:1. ..E2lb 9/00 aims intermediate the Minghead aimsarms 58 Field of Search ..175/384, 292, 342, carry their outerends hiiideis expansion teeth 175/382, 383, 299/61 80 which pivotoutward when the auger is rotated in one direction and inward when theauger is reversed. The [55] R f r it d expansion teeth and outermostboring head teeth are 90 apart and hence the head is supported so thatits UNITED STATES PATENTS tendency to bore a hole which is elliptictoward the 2,990,896 7/1961 Kandle ..17s/171 bottom is Overcom- Further,adjustment is Provided 1,848,192 3/1932 Newman ....175/384 for themaximum extent of outward pivotting of the 1,173,500 2/1916 Frank....175/384 expansion tooth holder for different casing wall 2,783,974 31957 Veasman ..175/384 thicknesses, 3,508,622 4/1970 Benetti et al...l75/384 X 4 Claims, 4 Drawing Figures PAIENTEU M22 1975 I JohnINVENTOR G. Bene HZ HEAD FOR HORIZONTAL BORING This invention relates toa new and improved head for horizontal earth boring. More particularly,the invention relates to a head which has essentially two parts onedisplaced approximately 90 relative to the axis of rotation of the headfrom the other. The forward portion has conventional earth boring teethwhich dig out the largest area of the hole being bored. Rearwardly, thehead has a second part having expansion holders with teeth to dig outthe perimeter of the holes thereby cutting clearance for the casing. Theexpansion holder has expansion teeth which are pivotally mountedthereon, so that when the head is rotated in normal cutting directionthe expansion holder and the teeth carried thereby pivot outwardly todig out the perimeter of the hole, but when the direction of rotation isreversed, the holders pivot inwardly to permit retraction of the headwithin the casing after excavation is completed.

Accordingly, a principal purpose of the present invention is to providea self-expanding, self-retracting clearance cutter, or expansion cutter,which is adjustable in the extent of expansion thereof.

Another and very important feature of the invention is the fact that theexpansion tooth holders are displaced approximately 90 from the cuttingtooth holders and this provides four point contact of the head with theground being excavated. The four point contact results in more truealignment of the hole being dug and also a more precise diameter. One ofthe problems of existing expansion head augers is that elliptic holesare cut because the expansion tooth holders are mounted on the same armsas the cutting tooth holders. Mounting expansion holders displacedrelative to the cutting holders in accordance with the present inventionkeeps the auger on center and maintains a more accurate grade. The fourpoint expansion more adequately supports the weight of the head on thesidewalls of the hole being excavated and thus helps to overcome thetendency for the auger to deviate downwardly from a straight line.

Anotherfeature of the invention is the provision of convenient means foradjusting the amount of outward expansion of the expansion teeth toaccommodate different outside diameters of casing and also to compensatefor wear of the teeth with the passage of time.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawingsin which similar characters of reference represent corresponding partsin each of the several views.

In the drawings:

FIG. 1 is a schematic, side elevational view showing a head inaccordance with the present invention and a portion of an auger to whichit is attached engaged in horizontal boring.

FIG. 2 is an end elevation of the structure of FIG. 1.

FIG. 3 is a fragmentary plan view of the arm on which the expansionholder is mounted partially broken away to reveal internal constructionand also to conserve space.

FIG. 4 is a fragmentary, side elevational view of a portion of FIG. 3.

The present invention is intended for use on an auger such asconventional auger 11 which has a central shaft 12 about which isdisposed one or more helical flights 13. On the working end of shaft 12is a head 14 which may be formed with a hub 16 attached to the end ofthe shaft 12. In the accompanying drawings a pilot bit 17 is attached tothe forward end of hub 16, and said bit may have removable bit teeth 18in accordance with U. S. Pat. No. 3,426,860 or may be otherwiseconstructed.

Extending radially, displaced 180 from each other, are digging arms 19and attached thereto on either side of the head are castings 21 held inplace by means of bolts 22 and having a plurality of sockets 23 for thepurpose of securing removable digging teeth 24. The position, number andshape of teeth 24 is subject to considerable variation. Various meansmay be used to hold the teeth 24 in place, such as the means shown in U.S. Pat. No. 2,968,880.

Immediately rearward of arms 19 are front and rear expansion arms 26,27. Arms 26, 27 are parallel to each other and angularly displacedrelative to arms 19 by (see FIG. 2). Arms 26, 27 are preferably spacedapart in the direction of the axis of shaft 12 a short distance byspacer 28 at the center. Additional spacers 29 are positioned betweenthe outer ends of the arms 26, 27. As best shown in FIG. 3, the outerspacers 29 are semicircular in shape and at least one end 31 is radiallydisposed. Between each end of arms 26, 27 is an expansion holder 32having a set screw 33 extending through projection 35 and bearingagainst end 31. Jam nut 34 holds the set screw 33 in the requiredposition of adjustment. Holder 32 pivots about pivot pin 36 which passesthrough the arms 26, 27 and is held thereby. The outer end of holder 32is provided with a socket 37 to receive an expansion tooth 38. Again,the shape and manner of holding tooth 38 is subject to variation, but apreferred shape and means is disclosed in U.S. Pat. No. 2,968,880.

The head 14 is intended for use in horizontal boring. In such use, theshaft 12 is rotated and moved axially by means of a machine (not shown)which also forces behind the head 14 a casing 41 which is very slightlyless than the size of the hole being dug and which supports the walls ofthe hole against cavitation and also supports the weight of the earthabove the hole and any structures thereon against collapse. In use ofthe device, the shaft 12 is rotated so that the head 14 turns inclockwise direction as viewed in FIG. 2. The pilot bit 17 tends tomaintain the direction of the hole being dug in a straight line. Thearms 19 are preferably slightly smaller than the internal diameter ofcasing 41 and dig out the earth as the head advances. The earth is thenconveyed to the opposite end of the auger by the flight 13, all as wellunderstood in the earth digging art. When the auger is turning indigging direction, the outer ends of the teeth 38 encounter the wall ofthe hole being dug and tend to pivot the holder 32 outwardly i.e.,counter-clockwise as viewed in FIG. 2 about pivots 36. The extent oftheir outward pivoting is adjusted by means of set screw 33 which bearsagainst end 31. Preferably, the teeth 38 dig a hole which is justslightly larger than the outside diameter of casing 41 so that thecasing may be driven behind the head as cutting continues. When theexcavation is completed, the shaft 12 is turned in an opposite directionand this causes the holder 32 to pivot inwardly thus permitting the headto be withdrawn within the casing 41 and removed.

Although the pilot bit 17 and the rigidity of shaft 12 tend to keep thehole being excavated by the head 14 in a straight line, neverthelessthere is a tendency for the direction of the hole to drift downwardlyunder the influence of gravity and this is augmented when hardstructures such as rocks are encountered which give a downward thrust.In the types of expansion heads which have hitherto been used, theexpansion tooth holders are mounted on the outer ends of arms 19 and donot satisfactorily overcome the tendency toward downward deviation.Another effect of downward deviation of the auger head is the tendencyto dig a hole which is non-circular, that is, which is deeper at thebottom than elsewhere around the perimeter and this may cause asubsidance of the ground surface above the hole being dug. It is one ofthe features of the present invention, as best shown in FIG. 2, thatthere are four points 42 at which the head 14 is supported by the wallof the hole being dug. These are, respectively, the two points at whichthe outermost teeth 24 engage the wall of the hole being dug and the twopoints at which the teeth 38 engage said wall. The four point suspensionis much more effective than two point suspension in overcoming thedeviation heretofore mentioned.

What is claimed is:

1. An earth auger head having an axis of rotation comprising a shaft, aplurality of first arms each carrying a plurality of first toothholders, first teeth in said first tooth holders, said first teethpositioned to bore earth at the end of a hole substantially transverseto said axis of rotation, a plurality of second arms spaced rearwardlyof said first arms and disposed substantially midway between said firstarms, said second arms comprising diametrically disposed, parallel,thin, narrow front and rear expansion arms, each said expansion armtransverse to said axis and spaced relative to each other along saidaxis, said first and second arms fixed to said shaft, an expansionholder mounting means on the outer end. of each said second arm disposedbetween said front and rear expansion arms, a pair of spacers betweensaid front and rear expansion arms spacing said expansion arms apart, anexpansion holder pivotally mounted in each said mounting means about asecond axis parallel to said axis of rotation, a second tooth in eachsaid expansion holder pivoting about said second axis between aretracted position inside the perimeter of the hole bored by said firstteeth and an extended position outside said perimeter, said second teethpositioned to dig the outside of said hole when in extended position,said second teeth when in extended position being substantially midwaybetween the two adjacent outermost first teeth when viewed in adirection parallel to said axis of rotation, said expansion holderspivoting to extended position when said head is rotated in one directionof rotation and to retracted position in reverse direction of rotationof said head.

2. A boring head according to claim 1 in which one saidspacer is locatedadjacent the outer end of said second arm and is formed with an abutmentand each said holder has a set screw engaging said abutment to limit theoutward extension of the second tooth held in said holder.

3. An earth auger head according to claim 1 which further comprises afirst abutment on each said second arm and a second abutment on eachsaid expansion holder, said abutments coming into contact with eachother to limit outward pivotal movement of said holder as said head isturned about its axis of rotation in first direction to limit theoutside diameter of the hole being bored. 7

4. A boring head according to claim 3 in which one said abutment isadjustable in position to adjust the size of said outside diameter.

1. An earth auger head having an axis of rotation comprising a shaft, aplurality of first arms each carrying a plurality of first toothholders, first teeth in said first tooth holders, said first teethpositioned to bore earth at the end of a hole substantially transverseto said axis of rotation, a plurality of second arms spaced rearwardlyof said first arms and disposed substantially midway between said firstarms, said second arms comprising diametrically disposed, parallel,thin, narrow front and rear expansion arms, each said expansion armtransverse to said axis and spaced relative to each other along saidaxis, said first and second arms fixed to said shaft, an expansionholder mounting means on the outer end of each said second arm disposedbetween said front and rear expansion arms, a pair of spacers betweensaid front and rear expansion arms spacing said expansion arms apart, anexpansion holder pivotally mounted in each said mounting means about asecond axis parallel to said axis of rotation, a second tooth in eachsaid expansion holder pivoting about said second axis between aretracted position inside the perimeter of the hole bored by said firstteeth and an extended position outside said perimeter, said second teethpositioned to dig the outside of said hole when in extended position,said second teeth when in extended position being substantially midwaybetween the two adjacent outermost first teeth when viewed in adirection parallel to said axis of rotation, said expansion holderspivoting to extended position when said head is rotated in one directionof rotation and to retracted position in reverse direction of rotationof said head.
 2. A boring head according to claim 1 in which one saidspacer is located adjacent the outer end of said second arm and isformed with an abutment and each said holder has a set screw engagingsaid abutment to limit the outward extension of the second tooth held insaid holder.
 3. An earth auger head according to claim 1 which furthercomprises a first abutment on each said second arm and a second abutmenton each said expansion holder, said abutments coming into contact witheach other to limit outward pivotal movement of said holder as said headis turned about its axis of rotation in first direction to limit theoutside diameter of the hole being bored.
 4. A boring head according toclaim 3 in which one said abutment is adjustable in position to adjustthe size of said outside diameter.